The present invention is directed to a powder charge operated setting device for driving fastening elements, such as bolts, nails and the like, into a hard receiving material, such as steel, concrete and the like, comprising a housing, a barrel mounted in the housing, a driving piston displaceably positioned in the barrel, and a guide bush located at and being coextensive with one end of the barrel. The guide bush forms a combustion chamber. The barrel is supported so that it can be rotated within the housing relative to the guide bush and the barrel has at least one outlet flow opening adjacent its rear end and the guide bush has an outlet flow duct which opens through the housing to the atmosphere.
To drive bolts, nails or the like into receiving materials of different hardnesses and strengths, the resistance to be overcome can vary greatly. Accordingly, there is a need for regulating the driving capacity of the device in accordance with the conditions experienced. In known setting devices operated by means of a powder charge, regulation is effected by using different strengths of the powder charge in the form of a cartridge or caseless charge. To avoid the necessary costly storage of the different strength propellant charges, it has been known to use a single strength propellant charge with means in the setting device for regulating propelling force.
In one known setting device, regulation of the propelling force is achieved by releasing some part of the propellant gases into the atmosphere. To regulate the output, the barrel, which is connected to the guide bush by means of screws, is axially offset relative to the guide bush by rotation so that a flow gap is produced between the rear end of the barrel and the inside of the guide bush which encircles it so that a portion of the propellant gases flows through the gap from the combustion chamber into the atmosphere passing through an outlet duct. By varying the size of the gap, the output can be controlled continuously so that the greatest output is achieved when the gap as closed and the output gradually is reduced as the gap is gradually opened.
One disadvantage of this known device is that the propellant charge residue relatively rapidly blocks the gap when it is open for reducing the propellant force because of the small width of the gap and thus alters the adjusted output and causes the barrel to be fixed relative to the guide bush.